The effects of ecological and genetic neighbourhood size on the evolution of two competing species

Summary Individual-based simulations were conducted to examine the effect of a small ecological neighbourhood (an area in which ecological processes such as density-dependent factors operate) and the genetic neighbourhood size (the size of an area from which the parents may be assumed to be drawn at random) on the coevolution of two competing species. For the simulations, individuals of two consumer species compete for two types of food organisms. Different genotypes (one locus and two alleles) have different efficiencies of food acquisition for different food types. Individual consumer organisms search for food within their home ranges and reproduce depending on the amount of food eaten. The dispersal distance of the offspring follows a normal distribution with a zero mean and _d standard deviation. Simulations were conducted by varying the home range size, mating area (area from where individuals choose their mates), standard deviation of dispersal distance, food generation time, the reproductive rates of food populations and the sizes and number of independent food populations. Food organisms reproduce either within one population or independently within 16 spatially divided populations. For all the simulations, competitive exclusion was the most frequent outcome and character displacement was the least frequent outcome. Through a 200-generation simulation, the two consumer species could co-exist longer and maintain a polymorphic resource use longer when the home range and mating size were small in 16 spatially divided populations than when random mating and homogeneous interaction occurred within a community (perfect mixing population). For perfect mixing populations, the frequency of character displacement increased as the food generation time became short and the reproductive rates of food decreased. It follows from the results that the sizes of the genetic and ecological neighbourhoods and the mode of resource dynamics can affect the evolution of two competing species.     

Longitudinal association of intimate partner violence and depressive symptoms

Purpose The association between intimate partner violence (IPV) and depression has been well established in cross-sectional research, but how IPV is associated with depressive symptoms over time has not been well studied.Methods Using the Central Pennsylvania Women''s Health Study, a population-based longitudinal survey of women aged 18–45 (N = 1,420), we performed a two-step logistic regression analysis. In step 1, the association of recent IPV exposure at baseline with depressive symptoms 2 years later was analysed adjusting for relevant covariates; in step 2, we additionally included positive coping strategies (social support, physical activity) and negative coping strategies (binge drinking/drug use, smoking) in the model.Results Baseline IPV was reported by 4.6 percent of the sample and was independently associated with depressive symptoms 2 years later (adjusted or 1.88, 95% confidence interval [CI] 1.02–3.45). The strongest predictor was depressive symptoms at baseline, which was associated with a fivefold increase in the likelihood of depressive symptoms at 2-year follow-up. Other predictors of future depressive symptoms were IPV at follow-up, older age, lower educational attainment, and lower household income. When we controlled for potential coping strategies in the model (step 2), the relationship between recent IPV and follow-up depressive symptoms was attenuated (adjusted OR 1.50, 95% CI 0.80–2.80).Conclusions Exposure to IPV increases the likelihood of depressive symptoms occurring two years later. Greater social support and binge drinking/drug use attenuates this association, suggesting that interventions focusing on coping mechanisms may serve to reduce the impact of IPV on future depression.     

杭州石荠苧的传粉、小坚果散布和邻群大小

作者在杭州葛岭对杭州石荠苧自然居群的传粉和小坚果散布进行了详细的观察和实验。结果显示 ,以 2 6 0个传粉昆虫的飞行距离推算的花粉绝对散布方差为 0 .0 82 m2 ,798个小坚果的亲子散布方差为0 .1587m2。在上述散布特点和异交率为 0 .92 5条件下的邻群面积为 2 .2 33m 2 ,在有效密度为 4 7.7株 / m 2的有效密度下的邻群大小为 10 6 .5株。杭州石荠以异交为主 ,非常有限的基因散布导致邻群面积很小 ,居群容易发生遗传分化。     

Correlations between forest stand diversity and landscape pattern in Otepää Nature Park, Estonia

Rank correlations between tree species diversity in forest stands and parameters of landscape pattern were calculated using data from 4933 locations in Otepää Nature Park. Stand diversity was characterised by the number of tree species in the stand formula and by the index of dominance of tree species’ coverage. Landscape diversity was characterised by locally calculated pattern parameters from three categorical map layers (1:10 000 base map, 1:10 000 soil map, combination of these maps) and from six numerical variables (elevation, slope angle, four channels of a Landsat 7 ETM image).A weak trend appeared for more diverse forest stands to be located in more diverse landscapes according to the base map. Forest stand diversity is also higher on steeper slopes and in places surrounded by slopes of varying steepness. The correlation between landscape diversity and biodiversity depends on the radius of the kernel in which landscape characteristics are calculated. Evidence of an indicative neighbourhood could be seen in many spatial relationships. The spatial correlation between stand diversity and indices calculated from the base map was most visible at distances ranging from 400 to 500 m; surface elevation and its variation correlates with stand diversity at distances of 100–200 m. Some relationships between forest diversity and landscape diversity that had a different sign of correlation in proximate and distant kernels can be interpreted as a need to standardise local landscape indices with the index values in a wider neighbourhood as a reference.     

NM+: software implementing parentage-based models for estimating gene dispersal and mating patterns in plants

NM+ is computer software designed for making inferences on plant gene dispersal and mating patterns by modelling parentage probabilities of offspring based on the spatially explicit neighbourhood model. NM+ requires a sample of mapped and genotyped candidate parents and offspring; however, offspring may optionally be assigned to single maternal parents (forming so-called half-sib progeny arrays). Using maximum likelihood, NM+ estimates a number of parameters, including proportions of offspring due to self-fertilization, pollen immigration from outside of a defined study site, parameters of pollen (and/or seed) dispersal kernels (exponential-power, Weibull, geometric or 2Dt) and selection gradients relating covariates (phenotypic traits) with male (and/or female) reproductive success. NM+ allows for missing data both in parents and in offspring. It accounts for null alleles and their frequencies can optionally be considered as estimable parameters. Data files are formatted in a table-like structure so they can be easily prepared in a spreadsheet software. By default NM+ is for studying plant populations, however, it can be used for any organism as long as data requirements and model assumptions are met. NM+ runs under Windows, but it can be launched under Linux using WINE emulator. NM+ can be downloaded free of charge from http://www.genetyka.ukw.edu.pl/index_pliki/software.htm.     

Focus: Sex and Gender Health: The Effects of Gender-based Violence on Women’s Unwanted Pregnancy and Abortion

The aim of this research is to understand how gender-based violence across the life-course affects the likelihood of abortion. Women outpatients (n = 309) revealed their exposure to four different forms of gender-based abuse: child sexual abuse (25.7 percent), teenage physical dating violence (40.8 percent), intimate partner violence (43.1 percent), and sexual assault outside an intimate relationship (22 percent). Logistic regressions revealed that no single form of gender-based abuse predicted abortion. The cumulative effect of multiple forms of abuse did increase the odds of having an abortion (OR = 1.39, CI = 1.13-1.69). Child sexual abuse predicted intimate partner violence (OR = 6.71, CI = 3.36-13.41). The cumulative effect of gender-based violence on women’s reproductive health warrants further research. Priority should be given to screening for multiple forms of victimization in reproductive healthcare settings.     

Neighbourhood effects in forests: implications for within-stand patch structure

1 MOSAIC, a spatially referenced Markov model was used to show how interactions among trees in a neighbourhood may influence the patch structure of forests. A series of two-species simulations were conducted with neighbourhood strength ranging from neutral (chances of species replacing each other independent of neighbourhood composition) to strong (chance of replacement for each species proportional to neighbourhood composition), and with neighbourhood sizes including 1–50 neighbours.
2 Neighbourhood strength was positively correlated with the degree of patchiness. Very high neighbourhood strength is necessary to form mono-specific patches composed of hundreds of individual trees. Intermediate neighbourhood sizes (5–12 neighbours) led to the most distinct patches where individuals were arranged so that contact between species was minimized.
3 Neighbourhood effects alone are unlikely to lead to large areas (several ha) dominated by one species. However, simulations showed that neighbourhood effects can augment small differences in the environment, resulting in large mono-specific patches.
4 Simulations with 4 and 5 species indicated that groups of species can interact to form spatially distinct communities, starting from a random mixture on a uniform environment. This implies that neighbourhood effects may be responsible for some unexplained variability in studies that attempt to relate environmental parameters to forest composition.
5 Patch structures that develop due to neighbourhood effects are usually not recognized by current vegetation classification schemes or by forest managers, and this lack of recognition could lead to the loss of certain natural spatial structures on forested landscapes.     

Mechanistic information on some inorganic and bioinorganic reactions from volume profile analysis

The value of the application of hydrostatic pressure as a variable in kinetics investigations designed to elucidate mechanisms of some inorganic and bioinorganic reactions is reviewed and appraised. This is accomplished by charting the development of this experimental approach that leads to the derivation of the volume of activation for an individual reaction, and in many cases to the establishment of a volume profile for an overall reaction. A selection of recent investigations in which volume profiles together with other information have been pivotal in understanding the relevant reaction mechanism is presented. Reactions highlighted are water exchange on both fully hydrated cations or on partially complexed aqua ions, transition metal complex formation, reactions of nitric oxide with a wide variety of iron complexes or iron-containing proteins, and potential oxidative catalysis employing hydrogen peroxide. Recent advances in theoretical calculations regarding solvent exchange on various ions, and particularly on lithium ions and beryllium ions are described.     

对应关系形成的一般分子机制

对应关系形成的分子机制的阐明对于在理论上深入了解对应关系本质和生命系统运行机制,在应用方面帮助人工利用、干预或构建对应关系具有重要意义．分子生物学的快速发展为对应关系的分子机制进行更深入和全面的认识提供了条件．本文在综合比较各种生物大分子基础上,提出系统性的多单体生物大分子模型理论,试图揭示对应关系形成的一般分子机制．该模型理论认为多单体生物大分子具有种类的高多样性,对应关系对多单体生物大分子高效完成各种生物学功能具有必要性,同时,多单体生物大分子的结构和性质也为对应关系的形成提供了可能性．对应关系的形成过程是一个相对独立的可分为3个阶段的复杂过程．在多单体生物大分子结构和性质基础上,从与配体间的识别机制、作用机制及亲和性三方面揭示了对应关系的形成机制．对多单体生物大分子产生对应关系的必然性、形成的分子机制的复杂性及在理论和应用方面的重要价值也进行了讨论．     

Socially isolated? How parents and neighbourhood adults influence youth behaviour in disadvantaged communities

William Julius Wilson’s model of adult joblessness, community disorganization and their effects on youth problem behaviour de-emphasizes the range in children’s outcomes across socially disorganized communities, and says little about the factors that influence this variation. It also does not address the processes by which family structure and relationships affect the well-being of African-American and poor youth. My work is part of a larger research agenda that has begun to address these issues by focusing on the differential rates of sexual activity among youth living in disadvantaged environments, and developing models to explain this variation. This work suggests that units of socially cohesive, stable adults exist among the social networks of successful children and families in poor neighbourhoods. It also points to the existence and functioning of alternative two-parent family structures and offers hypotheses for how family environment interacts with neighbourhood context to influence youth behaviour.     

Divide and conquer? Persistence of infectious agents in spatial metapopulations of hosts

Persistence of an infectious agent in a population is an important issue in epidemiology. It is assumed that spatially fragmenting a population of hosts increases the probability of persistence of an infectious agent and that movement of hosts between the patches is vital for that. The influence of migration on persistence is however often studied in mean-field models, whereas in reality the actual distance travelled can be limited and influence the movement dynamics. We use a stochastic model, where within- and between-patch dynamics are coupled and movement is modelled explicitly, to show that explicit consideration of movement distance makes the relation between persistence of infectious agents and the metapopulation structure of its hosts less straightforward than previously thought. We show that the probability of persistence is largest at an intermediate movement distance of the host and that spatially fragmenting a population of hosts is not necessarily beneficial for persistence.